The present invention relates to an alternating current generator having a plurality of sets of armature windings. More particularly, the alternating current generator of the present invention is suitable for use in a vehicle.
There have been used an alternating current (hereinafter referred to as a.c.) generator for a vehicle in which a rotor having field windings is disposed inside a stator having three-phase windings.
In this case, in order to increase the number of poles, a rotor is provided on the outer periphery thereof with a plurality of claw-shaped poles formed on a pair of magnetic cores. The armature of a stator is provided with 3 P slots (grooves) (one slot per phase and per pole) for the number of phases of the windings 3 and the number of poles P. The above-mentioned three-phase windings are disposed in these grooves and a tooth-shaped core is formed between a pair of neighboring slots or grooves.
However, since the a.c. generator for a vehicle having the claw poles has one set of three-phase winding and 3P slots (namely, one slot per phase and per pole), a magnetic flux 104 formed between poles 101 and 102 leaks through a tooth-shaped core 103 between two windings A as shown in FIG. 9a, when the poles 101, 102 of the rotor and the tooth-shaped core 103 of the armature take a relative position as shown in FIG. 8.
Such leakage of magnetic flux not only reduces the effective magnetic flux which contributes to electric power generation, but also generates pulsating magnetic flux.
Accordingly, this causes a magnetic noise to be increased, a generated voltage to fluctuate and an output waveform to be distorted, giving rise to ripples when a generated output is rectified into a direct current (hereinafter referred to as d.c.).
It has been demanded that such a magnetic noise is reduced all the more in a power source for a vehicle, etc. which power source feeds various electrical equipment utilizing electronic components and ICs. Further, a high quality direct current power source having less noise and voltage fluctuation due to a ripple, etc. is demanded.